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Pervskite solar cells have attracted extensive attention from researchers worldwide due to their rapid development and efficiency. Nevertheless, stability is still an issue that limits the advance of this technology. In this work, we present the fabrication and characterization of two-dimensional perovskites of the Ruddlesden-Popper's family (A)2(MA)n-1PbnI3n+1 (three different A-site large cations were investigated: A=n-propylammonium, t-Butylammonium or Benzylammonium). The modulation of the large organic cations increased the band gap of the materials and improved moisture and thermal stability, making it possible to fabricate PSCs. Even though the organic interlayers intrinsically reduce the transport properties of the devices and therefore lower currents are obtained in the layered systems, a remarkable efficiency of 10.35% was obtained for (BUA)2(MA)2Pb3I10, with superior stability, and therefore, it was possible to retain 68% of its initial value after 1700 h for devices without encapsulation. [ABSTRACT FROM AUTHOR]

• Mn2+ 4T 1 and Cd-Cd levels are formed into Mn-CdS after chalcogenide preparation. • Cd–Cd→Mn2+ 4T 1 carrier transitions improve the light-harvesting of the photoanodes. • The load of Mn-CdS QDs impacts on the charge transport ability of the photoanodes. • Mn2+ 4T 1 states provide a suitable band alignment in the composite heterostructure. • The Cd–Cd→Mn2+ 4T 1 interaction increases the electron lifetime into photoanodes. Low-band gap chalcogenides such as Bi 2 S 3 (<1.7 eV) have been widely used in optoelectronic devices such as quantum dot sensitized solar cells (QDSSCs), due to their high sunlight harvesting capability, absorbing low-energy photons close to the IR region. Nonetheless, Bi 2 S 3 offers a poor band alignment with large-band gap semiconductors such as TiO 2 , achieving low photoconversion efficiencies. Accordingly, we studied how the presence of both Mn2+ 4T 1 ligand field electronic states and structural defects as Cd–Cd energy levels produced during Mn-CdS synthesis influenced on the band structure and thereby, the charge carrier transport into co-sensitized boron, nitrogen and fluorine-co-doped TiO 2 nanotubes (X–Mn–Y–CdS–Bi 2 S 3). Carrier transfer pathways provided by both Cd–Cd defects and Mn2+ 4T 1 states allowed to obtain a suitable 0.7–Mn–4–CdS–2–Bi 2 S 3 based electrode, with a narrowed band gap of 2.16 eV and an appropriate II-type heterostructure. These features improved both the carrier separation and mobility from Mn-CdS/Bi 2 S 3 interface to co-doped nanotubes. Additionally, the electron lifetime into the composite photoanode was 10 times higher compared with a Mn2+-absent 4–CdS–2–Bi 2 S 3 material. Hence, the synergistic behavior between structural defects and ligand field electronic states explained here offers an insight for establishing adequate heterostructures to be useful in QDSSCs. [ABSTRACT FROM AUTHOR]